1. Field of the Invention
The present invention relates to a load-sensing device which is able to sense a load applied to the front of a vehicle.
2. Description of the Related Art
In recent years, it has been pointed out that a pedestrian collided with a vehicle may often be damaged by the portion near the vehicle's hood. Development of a vehicle has thus been proposed that has an airbag provided near the vehicle's hood to protect the pedestrian when the pedestrian is collided with the vehicle (for example, refer to Japanese Patent Laid-open Publication No. 2000-264146).
The airbag as described in the publication No. 2000-264146 and the like needs to be provided with a forward-sensing device provided at the front of the vehicle to sense the collision event. Such a forward sensing device includes a device which uses the infrared sensor and the like to sense the pedestrian approaching the vehicle to predict the collision, and a device which uses the load sensor and the like to sense the pedestrian collided with the vehicle. This specification refers to those of the forward sensing devices that can sense the collision with the load sensor as the load sensing devices.
The load sensor may preferably be provided on the front surface of an inner member such as the bumper reinforcement (or bumper reinforce), which is provided on the front side of the vehicle. An outer member such as the front-bumper cover, which is provided on the vehicle front-end side of the inner member, may preferably cover the vehicle front-side portion of the load sensor. FIG. 4 schematically shows a cross sectional view of such a conventional load-sensing device.
FIG. 4 shows a load sensing device 100 which includes the bumper reinforcement as an inner member 101, which has on its front surface the optical-fiber sensor as a load sensor 102. The front-bumper cover as an outer member 103 covers the vehicle front-side portion of the load sensor 102 and the inner member 101. It is noted that the inner member 101 has predetermined left and right portions that attach to the left and right front ends of a side member 105 of the vehicle frame.
In this load sensing device 100, a pedestrian collided with the vehicle may deform the outer member 103 from the front to back of the vehicle. The outer member 103 may then pressure the load sensor 102 provided on the backside of the outer member 103. This pressure can transmit the load to the load sensor 102 to allow the load sensor 102 to sense the collision. The outer member 103 located over the load sensor 102 may prevent the light load due to such as a pedestrian collided with the parked vehicle from being directly transferred to the load sensor 102, thereby preventing the airbag malfunction and the like.
As shown in FIG. 5, a buffer member 106 is generally provided on the back of outer member 103 to absorb the shock of the collision. In this case, however, the buffer member 106 can transfer the load applied to the outer member 103 to the inner member 101 and may not transfer sufficient load to the load sensor 102. Depending on the arrangement of the outer member 103 and the load sensor 102 and the like, the deformed outer member 103 may contact a portion 107 of the inner member 101 where the load sensor 102 is not provided and prevent the load applied to the vehicle from reliably being transferred to the load sensor 102. These cases may cause a problem that the load sensor 102 cannot reliably detect the load applied to the vehicle.